The present invention relates to cutaneous gas monitors and is directed more particularly to a feature used with the monitors that will alert an operator of the monitor to dangerous fluctuations in a body's metabolism.
Among the non-invasive patient monitoring instruments which have been developed recently is an instrument known as a cutaneous gas monitor. Gas monitors of this type make use of known gas detection techniques to measure the partial pressure of a gas, such as oxygen or carbon dioxide, which diffuses outwardly through a patient's skin. Cutaneous gas monitors have also been developed which simultaneously measure the partial pressure of both oxygen and carbon dioxide. One cutaneous gas monitor of the latter type is described in "Cutaneous Blood Flow and its Relationship to Transcutaneous O.sub.2 /CO.sub.2 Measurements", by A. V. Beran, et al., "Critical Care Medicine", Vol. 9, No. 10, pp. 736-741 (1981).
Prior to this invention, cutaneous gas monitors displayed only the current partial pressures for oxygen and carbon dioxide. The current partial pressure was manually logged at various intervals so that the operator of the monitor could observe both the patient's current partial pressure and review the trend of these partial pressures over time. This method for determining the trend in the partial pressure is not totally desirable. The logging of readings is both time consuming and tedious, and the determination of a trend cannot be quickly or easily performed.